#include<iostream>
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/wait.h>

#define MAXARGC 128
char* g_argv[MAXARGC];
int g_argc = 0;

#define FORMAT "[%s@%s %s]# "
#define COMMAND_SIZE 1024

const char* GetUserName(){
    const char* name = getenv("USER");
    return name == NULL ? "None":name;
}

const char* GetHostName(){
    const char* hostname = getenv("HOSTNAME");
    return hostname == NULL ? "None":hostname;
}

const char* GetPwd(){
    const char* pwd = getenv("PWD");
    return pwd == NULL ? "None":pwd;
}

std::string DirName(const char* pwd){
#define SLASH "/"
    std::string dir = pwd;
    if(dir == SLASH) return SLASH;
    auto pos = dir.rfind(SLASH);
    if(pos == std::string::npos) return "BUG?";
    return dir.substr(pos + 1);
}

void MakeCommandLine(char cmd_prompt[],int size){
    snprintf(cmd_prompt,size,FORMAT,GetUserName(),GetHostName(),DirName(GetPwd()).c_str());
}

void PrintCommandPrompt(){
    char prompt[COMMAND_SIZE];
    MakeCommandLine(prompt,sizeof(prompt));
    printf("%s",prompt);
    fflush(stdout);
}

bool GetCommandLine(char* out,int size){
    char* c = fgets(out,size,stdin);
    if(c == NULL) return false;
    out[strlen(out) - 1] = 0;
    if(strlen(out) == 0) return false;
    return true;
}

bool CommandPrase(char* commandline){
#define SEP " "
    g_argc = 0;
    g_argv[g_argc++] = strtok(commandline,SEP);
    while((bool)(g_argv[g_argc++] = strtok(nullptr,SEP)));
    g_argc--;
    return true;
}

void PrintArgv(){
    for(int i = 0; g_argv[i]; i++){
        printf("argv[%d]->%s\n",i,g_argv[i]);
    }
}

int Execute(){
    pid_t id = fork();
    if(id == 0){
        execvp(g_argv[0],g_argv);
        exit(1);
    }
    pid_t rid = waitpid(id,nullptr,0);
    (void)rid;
    return 0;
}

int main(){
    while(true){
        PrintCommandPrompt();

        char commandline[COMMAND_SIZE];
        if(!GetCommandLine(commandline,sizeof(commandline)))
            continue;
        CommandPrase(commandline);
        //PrintArgv();
        Execute(); 

    }

    return 0;
}
